Board Thread:Pokémon Help/@comment-31060136-20170805072508/@comment-30804097-20170805184325

No, DO NOT USE a Defense Reset on Raichu. Since you are EV-Training it in Defense (not recommended anyways - Raichu should have Speed and Sp. Atk, but eh), you do NOT want to use a Defense Reset on it, as it will get rid of all your Def. EVs.

Resets are for erasing the EVs of a Pokemon, not getting them more  efficiently. You should actually READ the description of the item and the name itself next time.